Aircraft with rotary wings



\ Dec. 25, 1951 c, PULLIN r 7 2,579,860

AIRCRAFT WITH ROTARY WINGS Filed July 29, 1947 10 Sheets-Sheet 1 1&9 J27 INVENTORS RT T0 RNEYS Dec. 25, 1951 p PULLIN ETAL 2,579,860

' AIRCRAFT WITH ROTARY WINGS Filed July 29, 1947 l0 Sheets-Sheet 2 sflg 1 Q a N Q r N 3% I l Y *2 AT TOHNEYS 'Dec- 1951 c. G. PULLIN ETAL 2,

AiRCRAFT WITH ROTARY WINGS Filed July 29, 1947 10 Sheets-Sheet 5 INVENTORS X m BY Q Dec. 25,1951

c. G. PULLIN' ETAL AIRCRAFT WITH ROTARY wmcs 1o sheets-sheet 4 Filed July 29, 1947 INVENTORS l L n 1951 c. G. PULLIN ET AL 2,579,850

AIRCRAFT WITH ROTARY WINGS l0 Sheets-Sheet 5 Filed July 29, 1947 IN VENTORS Q7W%%/ ATTORNEYS Dec. 25, 1951 c. G. PULLlN ETAL 2,579,860

' AIRCRAFT WITH RO'EARY WINGS Filed July 29, 1947 10 Sheets-Shee't 6 1951 c. G. PULLlN EIAL AIRCRAFT wrm ROTARY WINGS Filed July 29, 1947 10 Sheets-Sheet 7 ATTORNEYS Dec. 25, 1951 c. G. PULL]N' ETAL 2,579,860 r AIRCRAFT WITH ROTARY WINGS 4 Filed July 29, 1947 10 Sheets-Sheet s 75 7 49 v g v 70" r M 175 M w ATTORNEYS Dec. 25, 1951 c. G. PULLlN ETAL AIRCRAFT WITH ROTARY WINGS 10 Sheets-Sheet 9 Filed July 29, 1947 AT TOHNE YS Dec. 25, 1951 C PULUN ETAL 2,579,860

- AIRCRAFT WITH ROTARY wzmcs Filed July 29, 1947 10 Sheets-Sheet w 'AT TOR N E YS Patented Dec. 25,1951

2,579,850 I C E AIRCRAFT WITH ROTARY WINGS Cyril George Pullin, Tadburn,-Ampfield, and Kenneth Watson, Woolston, Southampton, England, assignors, by mesne assignments, to Autogiro Company of America, Philadelphia, Pa., a corporation of Delaware Application July 29, 1947, Serial No. 764,493 In Great Britain July 30, 1946 4 Claims. (01. 170-16025) The object of this invention is an improvement in the control mechanism of a helicopter, rotaplane or like rotary-winged aircraft having a lifting or sustaining rotor (or rotors) with vertical axis and means for collective (or mean) or/and cyclic pitch control of the rotor blades. The improvement with which this invention is concerned is in that part of the control mechanism forming part of the rotor hub assembly.

The improved mechanisms according to this invention for collective and cyclic pitch control respectively have the common feature that rotary displacement of a shaft element coaxial with the rotor hub, is converted into axial displacement (for collective pitch control), or rocking displacement about an axis perpendicular to the hub axis (for cyclic pitch control), of a spider or swashplate which rotates with the hub and is connected tothe rotor blades for effecting pitch angle variations, the conversionof rotary into axial or rocking displacement being effected by means of a Z-crank integral with the shaft element and carrying a loose ring, which is positively prevented from rotating relatively to the airframe and is substantially located with respect to the spider or swash-plate at one point and with respect to the airframeat another point, one of these points being on the axis of rotation and the other olfset therefrom, so that the resolved component in a fixed plane containing the shaft axis of the angular displacement of the loose ring caused by partial rotation of the Z-crank is communicated to the spider or swash-plate to effect the desired movement thereof.

For axial displacement of the spider or swashplate, the'loose ring is anchored to the airframe at a substantially fixed point offset from the "axis of the shaft element, causing the latter to move axially when it is rotated and transmit its axial movement to the spider or swash-plate.

li'or rocking displacement the loose ring is connected at a point offset from the axis of rotation to the non-rotary member of the swash-plate assembly, which member is mounted with freedom to rock about one axis not passing through the mentioned oifset point, or about two axes independently. This causes the oifset point to be displaced axially when the Z-crank is partially rotated and impart a. rocking displacement to the swash-plate assembly.

' The nature of the invention will be better understood from the following description of two specific examples with reference to the accompanying drawings, of which Figs. 1 to 6 are the w s accompanying the provisional specification. In the drawings: I

- Figs. 1 and 2 are mutually perpendicular axial sections of the first specific example of the inv nfi n l Figs. 3 and 4 are views similar to Figs. 1 and 2 2 respectively with the Z-cranks displaced through Figs. 5 and 6 are mutually perpendicular axial sections of the second specific example of the invention;

Figs. 7 to 9 are general arrangement views in plan, side and front elevation respectively of a three-rotor helicopter embodying control mechanism as shown in Figs. 1 to 4;

Figs. 10 is an enlargement of the forward part of the showing of Fig. 8, partly cut-away to show additional detail;

Fig. 11 is a part-sectional elevation of one rotor hub assembly of the helicopter of Figs. 7 to 9;

Fig. 12 is a part-sectional plan view of the mounting of one rotor blade on the hub assembly of Fi 11;

Figs. 13 to 15 are schematic representations of the control circuits of the helicopter of Figs. 7 to 10, Figs. 13 being a perspective view of the circuit parts connected to the cockpit controls, and Figs. 14 and. 15 being, respectively, front and side elevations of the circuit parts connected to the mechanism shown in Figs. 1 to 4;

Fig. 16 is a schematic perspective View of a single-rotor helicopter embodying control mechanism as shown in Figs. 5 and 6;

Fig. 17 is a sectional elevation on an enlarged scale of the rotor-hub assembly of Fig. 16.

In the specific example of Figs. 1 to 4, the collective pitch control mechanism is operated by the pulley I04; and the cyclic pitch control mechanism is operated by the pulley I25.

The pulley I04 has an integral hollow shaft I28, coaxial with the rotor hub and supported in a fixed housing I2'I, by bearings I29, in which it can rotate and slide axially. The shaft I28 has an enlargement I30 in the form of a Z-crank carrying an inclined ring I32 on a bearing I3I. The ring I32 is prevented from turning, when the pulley I04 and Z-crank I30 are rotated, by an integral arm I33 terminating in a ball I34 located in a socket I35, which can slide radially of the axis of shaft I28 in a pocket I36 formed in the housing I21. Rotation of the Z-crank I30 by the pulley I04 rotates the vertical plane in which the ring I32 is inclined without rotating the ring itself, and since the ring is anchored at the centre ofball I34 its centreis caused to shift axially of the shaft I28 causing this shaft to rise or fall.

The axial displacement of shaft I28 is transmitted through a bearing I31 to an extension sleeve I38 which is prevented from rotating by a splined joint I39 in which sleeve I38 is supported by the upper end of a tubular extension I 2'I of the fixed housing I21 lying coaxially within the rotor hub assembly. The sleeve I38 supports a rotary swash-plate I46 whose arms I41 are connected to rotor blade pitch changing levers, so that axial displacement of shaft I28 and the bearings I55.

3 sleeve I38 applies collective pitch angle variation to the rotor blades.

The swash-plate I46 rotates on bearings I44, I45 carried by a hollow centre member I43, which is supported in bearings I42 on trunnions MI integral with a fork I40 constituting an extension of the sleeve I38, which is prevented from rotating by the splines I39. The swash-plate is therefore free to rock about one horizontal axis only; namely the axis of trunnions I4 I, since the sleeve I36 does not rotate. Rocking of the swash-plate about the axis of trunnions I4I therefore proprovides cyclic pitch control of invariable phase whose zero is in the vertical plane perpendicular to the trunnion axis, since the arm I41 is advanced substantially 90in the direction of rotation of the rotor from the radial axis of the rotor blade to which it is connected; and this causes the plane containing the blade tip path, and consequently the lift vector, to reproduce the angular displacement of the swash-plate about the axis of trunnions I4I.

Rocking of the swash-plate I46 for cyclic pitch control is effected by rotation of the pulley I25, which is mounted on a shaft I48 supported coaxially in the shaft I28 and sleeve I38 by bearings I49, I50. .The shaft I48 terminates in an inclined crank I5I. in effect a Z crank, which carries, on bearings I52, an inclined ring I53 having trunnions- I54. Themember I43 has a second set of bearings I55, whose axis is perpendicular to that of the bearings I42 supported on the trunnions I4I and the trunnions I54 engage Rotation of the shaft I48 by the pulley I25 rotates the plane in which the crank I5I and trunnion ring I53 is inclined; and consequently the axis of the trunnions I 54 which cannot rotate, being located in plan by the centre member I43, is caused to rock about the axis of trunnions I4I and impart its rocking displacement to the centre member I43 and swash-plate I46.

The neutral position of both the collective and cyclic pitch controls is shown in Figs. 3 and 4. Figs. 1 and 2 show the positions taken up when the collective pitch control pulley I04 has been rotated through 90 in the direction for lowering the pitch by lowering the swash-plate I46. This is the minimum pitch position, 90 rotation in the opposite direction giving maximum pitch. Figs. 1 and 2 also show the positions attained when the cyclic pitch control pulley I25 has been rotated through 90 to give maximum inclination of the swash-plate I46 and maximum amplitude of cyclic pitch variation. 90 rotation of the pulley I25 in the reverse direction of course gives cyclic pitch variation of maximum amplitude and opposite sign.

If the pulley I25 could be rotated through 360, the cyclic pitch amplitude'would be varied from minimum, through zero (at 90 rotation), to maximum (at 180) and back through zero (at 270) to minimum (360). It will therefore be clear that the sign of the cyclic pitch control depends on which'half of the complete 360 rotationis used; and consequently the sign of the control canbe reversed by rotating the pulley through 180.

Since the control reverses at 90 displacement of the operating pulley I25 from the neutral position, and the ratio, change of cyclic pitch amplitude/control displacement is not constant, becoming progressively less as the 90 position is approached, it is preferred to use less than 180 of total displacement of the pulley I25. The

ratio, change of collective pitch angle/control displacement, are similar.

Axial displacement of pulleys I04 and I25 when the collective pitch control is operated is accommodated by giving a sufliciently long leadin to the operating cables.

Referring to Figs. '7 to 9, the helicopter has a body 50 provided with three outriggers 5|, 52, 53 arranged at angles of 120 in plan, the outrigger 53 being in the fore and aft vertical plane of symmetry of the helicopter whose normal. (forward) direction of travel is indicated by an arrow in Fig. 7. The inboard parts 5| to 53, of. the outriggers are constructed as lattice girders and, their outboard parts 5I 52 53 are of monocoque construction. The outriggers support three identically similar three-bladed rotors 54, 55, 56 having identically similar blades 51; and all three rotors rotate counter-clockwise as seen from'above, the directions ofv rotation being indicated by arrows in Fig. 7. All three rotors are driven by a single engine 58 through distribution gears housed in a distributive gear-box 59 and through high-speed transmission shafts I9I, I92, I93 respectively. At the ends of the outriggers are mounted gear-boxes I94, I95, I96 containing speed-reduction gearing through which the hubs I91, I98, I 99 of the rotors are driven.

The body proper is covered with a skin 48; the pilots cabin is in the fore part of the body and is indicated at 49 in Figs. 7 and 10.

Referring now to Figs. 11 and 12, each hub I91 (I98 or I99) is connected by a screwed joint 236 with a sleeve 233 which is rotatably supported by a bearing 232 in the appropriate gear box I94 (I95 or I96) containing gearing by which the drive. is transmitted from shaft I (I92 or I93) to the sleeve 233. The lift of the rotor is transmitted from sleeve 233 to the gearbox I94 (I95 or I96) through the. bearing 232.

The hub I91, I98 or I99 of each rotor has three flapping pivotpins I56, whose axes intersect the hub axis at included angles. of Thus there is-no flapping-pivot offset. Each flapping pivot pin carries. a drag link I51 on an inboard needle roller bearing I58 and an outboard double-row self-aligning. roller bearing I59. The drag link is forked and its fork-ends I6I support coaxial drag pivot pins I62, on which the ends I65 of a forked blade root stub I66 are journaled. The blade root, which consists of four elements I69, I10, HI and I12, bolted together at I13, rotates on. the stub I66 for pitch' angle variation, being mounted by means of a bearing assembly comprising a taper roller thrust and radial bearin I14, 2. taper-roller pre-load bearing I15, and a pre-loading collar I16 with buttress threads, screwed onto the stub I66. 7

The-diaphragmv element, "I, of the blade root carries an: inboard extension I11, which is coaxial with the blade root and is connected'to a pitchchange torque tube I18 by a universal Joint; I19, I80, I8I centred on the dragpivot axis.

The inboard end of the torque-tube I18 is supported by means of a. needle roller bearing "I85 on a stud I84, screwed into the drag link I51; and the torque-tube has an integral lever I86 whose forked end carries spherical seating elements I81 of a ball joint, of which the ball I88 is formed on the end of a vertical link I89, as shown in Fig. 11, which also shows that the other end of the link I89 is connected by a ball joint I90 with one of the arms I41 of swash-plate I46 (see also Figs. 1 to 4).

The centre of the ball joint I81, I88 is aligned in plan on the axis of the flapping pivot pin I51, thus obviating any interaction between flapping and pitch angle, and this alignment is maintained, notwithstanding displacements of the blade on the drag pivot by the circumstance that the alignment of the torque-tube I18 with respect to the drag link is maintained constant by the spigot bearing I84, I85 and the universal joint I19l8I, centred on the drag pivot axis, which joint accommodates displacements about the last named axis, while transmitting pitchchanging displacements to the rotor blade.

The housing I21, shown also in Figs. 1 to 4, is mounted coaxially with the gear-box I94 (I95 or I96), being secured to it by a flange I21 and the extension I21 is enclosed within the gear-box and hub I91 (I98 or I99).

Referring now to Figs. and 13 to 15, a control column 62 is pivoted at 63 for fore and aft movement on a rocking shaft 64 supported in bearings 65. Fore and aft movement of the control column is transmitted by means of a pushpull rod 66 to the vertical arm of a bell-crank 61; and lateral movement of the control column is transmitted by the rocking shaft 64 and a crank 68 fixed thereto, through a link 69, a bell-crank I0 and a push-pull rod 1|, to the vertical arm of a bell-crank 12. The bell-cranks 61, 12 are pivoted on a bracket 13 secured to a vertical pillar 14, and their horizontal arms are respectively connected by vertical links and 16 with arms 11 and 18 of a horizontal spider 19, the arm 11 being fore and aft and rearwardly directed and the arm 18 being at right angles to arm 11 and directed to port. The spider is mounted con' centrically on pillar 14 by means of a universal joint 81 (here shown as a ball joint, which will be provided with means (not shown) preventing rotation of the spider) and it will be seen that the linkage described transmits fore and aft and lateral rocking of the control column to the spider, so that the latter repeats the displacements of the control column.

A pitch-change lever 82 is mounted on a transverse rocking shaft 83 supported in bearings 84 and carrying a crank 85 which is connected by a push-pull rod 86 to the vertical arm of a bell-crank 81, whose horizontal arm is connected to the pillar 14, which slides vertically in guides 88. Operation of the pitch-change lever thus raises and lowers the spider 19 bodily.

The spider 19 has two other horizontal arms 69 and 90 disposed at angles of 120. with arm 11 and with one another. The arms 89, 90, 11 are connected at equal radii from the centre of the spider with vertical links 9I, 92, 93 whose other ends are respectively connected to cranks 94, 95 and 96, operating pulleys 91, 98 and 99, which carry cables I00, I M and I02 respectively. The latter are led over jockey pulleys I03 and operate pulleys I04, I05 and I06 coaxial with the several rotor hubs. These pulleys operate the collective pitch control mechanisms of the several rotors, as described with reference to Figs. 1 to 4. It will be seen that raising or lowering of the spider 19 in response to operation of the pitch change lever 82 applies equal rotations in the same sense to all three pulleys I04, I05 and I06 to vary the collective pitch angles of all the rotors equally in the same sense; and that rocking of the spider on its universal joint in response to movements of the control column applies differential rotations to the pulleys. Fore and aft movement applies equal rotation in the same sense to the pulleys I04 and I05, to increase (or decrease) equally the collective pitch angles of rotors 54 and 55, and a contrary rotation of greater extent to the pulley I06, to vary the collective pitch angle of rotor 56 in the opposite sense, the rotations of the several pulleys being proportional to the projections of arms 89, and 11 on the pitching plane; and lateral movement of the control column applies: equal and opposite rotations to pulleys I04 and I05 to apply equal and opposite rotations to pulleys I04 and I 05 to apply equal and opposite variations to the collective pitch angles of rotors 54 and 55, and no rotation to pulley I06.

It will readily be seen that the spider mechanism illustrated in Fig. 13 ensures that for any displacement of the control column the algebraic sum of the rotations imparted to pulleys I94, I05 and I06 is zero, and hence, the total lift of the three rotors remains constant, at least in hovering flight.

A rudder-bar I61 (see Figs. 10 and 13) is mounted on a vertical pillar I08, which is supported in a bearing I09, and carries a crank IIO connected by a push-pull rod I II to the vertical arm of a bell-crank II2, whose horizontal arm is connected by a vertical link II3 with a twoarmed lever II4 pivoted on a fore and aft horizontal axis at H5. The arms of lever II4 are respectively connected by push-pull rods H6, H1 with cranks H8 and I I9 (see Fig. 141) operating pulleys I20 and I2! carrying cables I22, I23 which are led over jockey pulleys I24, and operate pulleys I 25 and I 26 coaxial with the hubs I91, I98 of the side by side rotors.

Movements of the rudder-bar apply equal and opposite rotations to the pulleys I25, I26 the direction of rotation depending on whether port or starboard rudder is applied. The pulleys I25, I26 operate the cyclic pitch control mechanisms of the rotors 54, 55. The mechanism, which has been described with reference to Figs. 1 to 4, varies the amplitude and sign of the cyclic pitch variation, but not its phase, the zero phase being substantially in the fore and aft azimuth. Variation of the cyclic pitch amplitude therefore varies the inclination of the lift vector in the fore and aft azimuth, and consequently varies the horizontal component of the lift in that azimuth; and the opposed rotations of pulleys I25, I26 therefore introduce opposed or differential cyclic pitch control of the two side by side rotors, giving equal and opposite variations of the fore and aft horizontal components of the lift, producing equal yawing moments of the same sign, without introducing any transverse force.

In the specific example of Figs. 5 and 6, there are three concentric control shafts, coaxial with the hub, viz. I 0, II and I2. The inner shaft I0 supports a rotary swash-plate I8 on a gimbal mounting I3, I4, I5 which carries a ring I6 constituting the centre member (non-rotative) on which the swash-plate rotates on bearings I1. The swash-plate has arms I9 connected in the usual way to the pitch-change levers of the rotor blades (not shown) by ball-joints and links 2|.

The intermediate tubular shaft terminates in an inclined or Z crank 22 carrying an inclined ring 23 on a bearing 24, and. the outer tubular shaft l2 terminates in an inclined crank 25 carrying, an inclined ring. 25 on. a bearing 2?; and rings 23;. 26 are respectively provided with arms 28 and 32 in mutually perpendicular vertical planes,- which are respectively connected with the gimbal ring l4 and: with the swash-plate centering ring [5 by links 30, 34 pivoted to the rings I4, [5 at 3|, 35 and connected to the arms 28, 32 by ball-joints 23, 33 respectively.

'It will be seen by analogy with the preceding example that rotation of shafts H and I2 rocks the rings 23-, 26 in mutually perpendicular planes and. these rocking displacements are transmitted by the linkages 28 to SI and 32 to 35 to the swash-plate assembly I 6, l7, H3.

The shafts I I, I2 are respectivelyprovided'with operating pulleys 36, S1 rotation of which dis places the swash-plate independently in two mutually perpendicular planes.

Collective pitch control is eiiected by raising and lowering the inner shaft Ill axially, for which purpose, in this example, an ordinary bell-crank 38 and operating rod 3?:- are provided instead of the Z-crank arrangement of the preceding example; which may be incorporated aslan alternative, e. g. by providing a further coaxial sleeve enclosing the sleeve l2 and having a Z-crank carrying a loose ring anchored as at lfi i'in Figs 1 to 4 the additional sleeve being provided with a (third) operating pulley and an abutment on a thrust bearing mounted on sleeve l2 by means of. which the swash-plate assembly is raised and lowered by the additional sleeve, when the latter is partially rotated.

The installation of. the control mechanism shown in Figs. 5 and 6 in a typical single-rotor helicopter is illustrated in Figs. 16 and 17 and comprises a body 35 rotor mounting pylon structure H,. and asecondary gear-box E2. which houses the bearings supporting a rotor hub 53, on which are articulated rotor blades 44. The rotor is driven by an. engine 45. through. gears, contained in a primary gear-box All, and a transmission shaft 4?, which drives the hub 43 through gears 6i 6! enclosed in the secondary gear-box. 42.

The rotor blades 44 are articulated by means of drag pivots 2 it, drag links 2 l8 and flapping pivots 2H to the hub 43. The blades M are mounted on their root stubs by means of pitchevarying pivots (not shown) and have integral levers 255ebeing transmitted through a push-pull rod 2&3

and a crank 294 to a pulley 2'05 carrying an endless cable 206 which passes over jockey pulleys 20 to the pulley '36 previously described. The rocking shaft" 202 carries a; pulley 208 which transmits lateral rocking motion of the control column to the pulley 31 by means of. an endless cable 269, which passes over jockey pulleys 218.

The rod 39, which. as previously explained controls the collective pitch of the rotor blades, is connected by means of a bell crank 2| l, rod; 2l2, bell crank '2 i3 and rod 2 [4 with a crank. 2 I5 rigid with a. pitch leveri" 216.

These control circuits operate in the conventional manner, which is. well understood in the art, and no further explanation of their opera.- tion is needed;

It is to be understood that the accompanying drawings, illustrative of specific examples of ap paratus embodying the invention, arenotto scale and are largely of a conventional nature; no significance is to be attached to the dimensions of anypart shown, nor are these drawings in any way to be looked on as a guide to detail design; except in so far as the text. of the description may otherwise direct.

We claim:

1. In a helicopter or like rotary-winged aircraft having a lifting or sustaining rotor with av rotor hub,- mechanism for controlling the pitch angles of the rotor blades of the lifting or sustaining rotor including a rotative swash ring connected to the rotor blades and being tiltable and displaceable axially of the rotor, a nonrotative swash ring on which the rotativering is jjournalled,v a gimbal ring for mounting" the nonarotative swash ring, a vertically movable support. for the gimbal ring, a shaft coaxial with the rotor hub and provided with a Z-crank' carrying a loose ring, and a connection between said loose. ring and the gimbal ring providing for angular tilting of the gimbal ring and thus of the swash rings.

2. A, construction in accordance with claim 1 and further including a second shaft arranged coaxially oi the rotor and provided with a Z- crank. carrying a loose ring, and a connection between the gimbal ring and'the second loose ring providing for angular tilt of the gimbal ring upon rotation of the second shaft.

3. A constructionin accordance with claim 2 in which. the connections between said loose rings and said gimbal ring are angularly offset from.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Country Date Germany Jan. 31, 1941 Number 

